Experimental verification of nanofluid shear-wave reconversion in ultrasonic fields

Abstract

Here we present the verification of shear-mediated contributions to multiple scattering of ultrasound in suspensions. Acoustic spectroscopy was carried out with suspensions of silica of differing particle sizes and concentrations in water to find the attenuation at a broad range of frequencies. As the particle sizes approach the nanoscale, commonly used multiple scattering models fail to match experimental results. We develop a new model, taking into account shear mediated contributions, and find excellent agreement with the attenuation spectra obtained using two types of spectrometer. The results determine that shear-wave phenomena must be considered in ultrasound characterisation of nanofluids at even relatively low concentrations of scatterers that are smaller than one micrometre in diameter.

Effective dynamic properties of random complex media with spherical particles

“…Recent numerical investigation by Pinfield's group 41 and experimental validation (on acoustic attenuation) 42,43 have demonstrated that the resonance peak observed in the attenuation against frequency curve for the coherent compressional wave also shifts to higher Reðk s aÞ as the concentration increases. This is consistent with the findings here on the effect of concentration on the effective density, which influences the effective compressional wavenumber.…”

“…The previously neglected multi-mode conversions have been demonstrated to be significant in nanoparticle suspensions and the new model applied to such systems 41 presents a greatly improved agreement with experimental data. 42,43 Further experimental evidence of the FIG. 1.…”

Analysis of MHD micropolar nanofluid flow and heat transfer between a porous plate and a nonporous plate filled with porous medium

“…3,4 The behavior of nanofluids is found to be very critical in deciding their suitability for convective heat transfer applications. [5][6][7] Choi and colleagues 8 show thermal conductivity enhancement and measured the thermal conductivity of nanofluids. The heat transfer and flow of nanofluid in porous media have received a great deal of attention in recent years, mainly due to the large number of relevant technical applications, which include fluid flow in geothermal reservoirs, catalytic reactors, separation processes, and nuclear waste storage.…”

“…Nanofluids have novel properties that make them potentially useful in many applications in heat transfer including microelectronics, fuel cells, pharmaceutical processes, thermal therapy for the treatment of cancer diseases, chemical and metallurgical processes, power generation, microproduction, transportation, cooling, heating, air‐conditioning, ventilation, hybrid‐powered engines, engine cooling/vehicle thermal management, grinding, machining, and in boiler flue gas temperature reduction . The behavior of nanofluids is found to be very critical in deciding their suitability for convective heat transfer applications . Choi and colleagues show thermal conductivity enhancement and measured the thermal conductivity of nanofluids.…”

“…Much research on flow in porous media has been done. The Darcy law expresses the relationship between the superficial velocity with the pressure drop, though this is applicable only under the assumption of slow, viscous flow conditions . Darcy measured the bulk resistance to flow of an incompressible fluid through a solid matrix as compared to the resistance at and near the surfaces confining this solid matrix.…”